Cross-sectional imaging plays a pivotal role in the diagnosis, staging, and follow-up of mucormycosis. CT and MRI are the primary modalities used to detect:

• Sinus and soft tissue involvement, often presenting as mucosal thickening or non-enhancing necrotic areas.
• Orbital extension, characterized by proptosis, muscle involvement, and/or orbital apex syndrome.
• Intracranial spread, identified by cavernous sinus thrombosis, cerebral infarcts, or abscess formation.
• Multisystemic involvement may manifest as pulmonary involvement, spread to the gastrointestinal tract, or renal involvement, further complicating management.

CT findings:

Sinus Involvement: Non-enhancing soft tissue thickening in the paranasal sinuses, often with bone destruction of the sinus walls. The infection can affect multiple sinuses with heterogeneous opacification.

Bony Erosion: Destruction of the nasal septum, orbital walls, or palate is indicative of invasive disease.

Intraorbital Spread: Proptosis, orbital fat stranding, and extraocular muscle thickening suggest orbital involvement.

MRI findings:

Sinuses and nasal cavities: T1 hypointense and T2 isointense to hypointense signal in the affected sinuses due to necrosis and hemorrhage. Contrast-enhanced MRI often shows poor or absent enhancement in necrotic areas - black turbinate sign.

Orbital involvement: Orbital fat shows increased signal intensity on T2, with possible involvement of the optic nerve and extraocular muscles.

Perineural spread: Extension along the trigeminal nerve or other cranial nerves intracranially.

Cerebral extension: T1-weighted images may reveal infarcts or hemorrhages secondary to vascular invasion and thrombosis. Contrast-enhanced sequences can detect meningeal enhancement or abscess formation. Involvement of the cavernous sinus and internal carotid artery may be seen, leading to carotid occlusion, infarction, or cavernous sinus thrombosis.

Pulmonary involvement is common in hematologic malignancies or transplant recipients. Imaging often reveals nodules with surrounding ground-glass opacity (halo sign on CT), representing angioinvasive fungal lesions. Over time, lesions can cavitate, showing an air crescent sign. Pleural effusions and consolidation may also occur.

Gastrointestinal mucormycosis is rare and often presents with non-specific symptoms like abdominal pain or bleeding. Imaging may show bowel wall thickening, pneumatosis intestinalis, or perforation, indicative of ischemia or necrosis.